92 



SEWAGE AND ITS PURIFICATION 



The nitric nitrogen and the ammoniacal nitrogen present in 

 the filtrates when the bacterial samples were collected are 

 shown in the following table : 



Nitric nitrogen 

 Ammoniacal nitrogen 



Tank Effluent. 



Filtrates. 



Nil. 



12-3 



C 



5-48 

 4*56 



D. 



II-6 

 2-05 



F. 



10*96 

 3-28 



It may therefore be concluded that the greater the aeration 

 and nitrification, the less is the possibility of the survival of 

 pathogenic organisms. 



Johnson and Whipple have shown ^ that the colon bacillus is 

 taken up by fish, and multiplies rapidly in their intestinal tract, 

 whereas fish caught in an unpolluted water failed to reveal the 

 presence of this organism. It would seem possible, therefore, 

 that fish, having taken up the colon bacillus from a polluted 

 water, might migrate to a water of comparative purity, wherej 

 they would naturally discharge the greatly increased number oi 

 these organisms. If the colon bacillus can be thus easily 

 transferred from one water to another, the transportation of thai 

 typhoid bacillus may be considered quite as likely. This mayj 

 explain the phenomenon frequently noted where B. coli com- 

 munis is found in comparatively large numbers in waters' 

 apparently open to but remote chances of faecal contamination. 



In the subcutaneous injection of guinea-pigs (Royal Commis- 

 sion, Second Report, 1902, p. 57) Dr. Houston found that crude 

 sewage always produced a local reaction, and not uncommonly"' 

 death. Street washings, storm water, overflow liquid from 

 sewage works, and, in general, bad effluents, were apt to be 

 pathogenic. Good effluents could be injected in relatively 

 large amounts without producing a fatal result. His opinion 



^ American Public Health Association, Journal of Infectious Diseases, Chicago. 

 March 19, 1904. 



